The present invention relates generally to wireless networks and more specifically to multiple overlapping wireless networks with multi-mode mobile nodes.
The existing IEEE 802.16e and IEEE 802.11k draft standards both define a method where an AP (Access Point) can determine a list of neighbor APs and advertise the list of neighbor APs to MNs (Mobile Nodes). A neighbor AP is consistently identified by an 802 radio port address or “APRID”, in both the 802.16e and 802.11k draft standards.
Currently, a WiFi AP or WiMax AP discovers neighbor APs, with the same radio type, in a couple ways:
1) An AP directly discovers a neighbor AP by scanning multiple channels for messages sent by the neighbor AP; or
2) MNs scan multiple channels for nearby APs and report scanned APs to parent APs.
The IEEE 802.16e draft standard defines a method where a parent WiMax AP can request or direct a child MN to roam to a neighbor WiMax AP. For example, a parent AP may direct a MN to roam to a neighbor AP that is more lightly-loaded.
WiFi APs that provide access to a “distribution network” (i.e. such as a WMAN) are grouped into an “Extended Service Set” (ESS) and share one or more Service Set Identifiers or SSIDs. A MN must be configured with a matching SSID to join the Extended Service Set (ESS). WiFi APs advertise the list of supported SSIDs in Beacons and Probe Response messages; so that MNs can easily determine the set of APs that belong to the same ESS. The 802.16 draft standard does not provide a comparable method for grouping WiMax APs into an ESS. Presumably, only one WiMax Service Provider can provide WiMax coverage in a give area.
A WMAN may contain multiple “wireless domains”, as described above. In practice, a wireless domain typically corresponds to a set of IP subnets. Inter-wireless-domain roaming is generally more “expensive” than intra-wireless-domain roaming. For example, when a MN roams to a new parent AP in a different domain, the MN may lose access to its current home subnet.
A rogue AP may masquerade as an authorized AP by spoofing the authorized AP's SSID(s) and APRID in AP advertisement messages. For example, a rogue WiFi AP may send 802.11 Beacon messages that contain the SSID and APRID (i.e. 802.11 BSSID) of a different authorized WiFi AP. A Management Frame Protection (MFP) protocol can be used, in part, to authenticate Beacon and Probe Response frames with a secret group key that is shared by authorized APs and authorized MNs. The MFP protocol enables WiFi MNs to detect and avoid rogue WiFi APs. A MN reports a detected rogue AP to its parent AP, so that the parent AP can generate an alert.
Multi-mode mobile nodes (MNs) are capable of operating with two (or more) radio types. Typically, a multi-mode MN scans channels on the networks it is configured to operate, e.g. scan WiMax (i.e. IEEE 802.16) channels and scan WiFi (i.e. IEEE 802.11) channels. A problem with current systems is that the networks (e.g. WiMax and WiFi networks) operate totally independently, which can cause problems for a multi-mode radio. For example, while connected to a parent AP in one mode, it must continually scan channels for the other mode because the parent AP is unaware of AP's in the other radio mode. As another example, a multi-mode radio might be operating in WiMax mode when an alert is sent for a rogue AP on the WiFi network, causing it to miss the alert and when the MN changes to WiFi mode, the MN may attempt to associate with the rogue AP because it missed the alert.
Although the above discussion refers to networks with WiMax and WiFi, those skilled in the art can readily appreciate that the concepts described herein are readily adaptable to encompass any combination of radio technologies such as GSM, Bluetooth and CDMA.